There has been a prolific growth in the production of ICs and an increase in the number and type of products that incorporate ICs. Some ICs, such as memory chips and some processors, are made in such large quantities that they are sometimes regarded as commodity items.
ICs typically consist of a semiconductor substrate or die that is mounted in a package. The package is often a plastic and/or ceramic casing that distributes the densely arranged contact pads of the die to an array of pins or other extensions that extend from the package and permits the IC to be mounted to a printed circuit board or other substrate. Note that while lead or pin packages are referred to predominantly herein, the present invention applies as well to ball grid array, beam lead, flip-chip mounting and other IC mounting techniques.
Typical development of an IC includes the steps of design, fabrication, prototype testing, redesign (modification based on test results), prototype re-testing and larger scale manufacture. It is critically important at all stages of the IC development and production chain, i.e., prototype development through quality assurance, to provide rapid and accurate testing of an IC.
FIG. 1 illustrates a representative prior art testing assembly for testing packaged ICs. The testing assembly 10 includes a base 12 having a test socket 14 and a lid 20 having an IC mounting mechanism 30. In the perspective of FIG. 1, socket 14 is shown as extending above base 12 so that it may be seen, though it is typically recessed below the top surface of base 12.
In use, an IC 18 is positioned over socket 14 such that pins 17 align with corresponding holes 15 in the socket. The hinged lid 20 is shut and the IC mounting mechanism is actuated to assert a distributed force onto the IC that pushes the pins of the IC a sufficient distance into holes 15. The IC mounting mechanism includes a screw-based positioning mechanism 31 that determines the distance by which the pins are seated into the holes and a pressure plate 22 that more evenly distributes the force of the positioning mechanism.
The positioning mechanism includes a cylindrical screw 32, an annular disk 34 and coupling screws 35. These components engage a threaded hole 24 in lid 20 and a stop pin 26 mounted on the top of lid 20. The cylindrical screw 32 threads into hole 24 and the annular disk has a ¾ rotation length recessed groove 36 on its underside that fits over pin 26. The relative position of the annular disk and the cylindrical screw are set by screws 35 with the cylindrical screw threaded into hole 24 and the annular disk mounted such that groove 36 is positioned about pin 26. The relative position of the cylindrical screw and the annular disk is maintained by the coupling screws 35. To seat an IC into socket 14, the annular disk is turned ¾ rotation (the length of groove 36) which pushes the pressure plate down an appropriate distance to securely seat the IC on the socket in a manner that does not damage pins 17 or other aspects of the chip, package or test equipment.
To establish the appropriate depth of cylindrical screw 32 below lid 20, it is necessary to connect these two components at a first relative position, mount an IC in test assembly 10 and run an IC test program to confirm whether all of the pins 15 are properly contacted. If the pins are not properly contacted, then coupling screws 35 are unscrewed, the relative position of the annular disk and cylindrical screw is repositioned, screws 35 are re-tightened, the lid is closed, the annular disk is turn ¾ rotation to mount the IC onto the socket, and the IC pin seating test program is run again. This multiple step setting procedure is repeated until the annular ring and cylindrical screws are positioned to appropriately seat an IC each time.
This positioning, screwing, testing, repositioning, etc., procedure is undesirably time consuming and adds significantly to the cost of prototype assessment and IC production. The disadvantageous aspects of this multiple-step test setup procedure are compounded by the fact that different ICs have different sized packages and the multiple-step test setup procedure must necessarily be repeated for each type of IC under test.
A need thus exists for more efficiently and economically accommodating different sized ICs and IC packages in IC test equipment.
Another relevant aspect of the present invention is providing a security mechanism that prevents a test operator from inadvertently opening a test assembly, i.e., opening the assembly before releasing the pressure asserted by the IC mounting mechanism. Opening the lid before rotating the mounting mechanism back ¾ rotation (or the like) can cause the lid to fly open with significant force, potentially causing damage to the operator or equipment. Furthermore and perhaps more importantly, if the positioning mechanism is not repositioned upward before mounting, then as the lid is pivoted closed, the portion of the pressure plate closest to the hinge will contact the IC first and force the IC onto the socket at an angle, as opposed to a uniform force from above. Mounting an IC at an angle is far more likely to cause pin damage and mis-alignment.